With increasing performance of the electronic devices, various heat dissipating structures or heat dissipating devices for the electronic devices are developed vigorously. For example, a fin-type heat sink is one of the widely-used heat dissipating devices. The fins of the fin-type heat sink usually have the same specification and are orderly arranged. Generally, the heat dissipating efficiency of the fin-type heat sink is positively correlated with the heat transfer area of the fins. Recently, the general trends in designing the heat dissipating devices are toward small size and light weightiness. In other words, it is important to increase the heat dissipating efficiency while meeting the requirement of small size and light weightiness.
For example, a fin-type heat sink was disclosed in Taiwanese Utility Model Patent No. M270414, which was filed by the same assignee of the present application. In this patent, two kinds of fins with different sizes are alternately arranged along a specified direction. Since the wind resistance at the airflow inlet is reduced, the ambient airflow can be introduced into the heat sink more easily. That is, this fin-type heat sink has enhanced heat dissipating efficiency and reduced weightiness. Although the design of alternately arranging different kinds of fins can overcome the drawbacks of the conventional technologies, the fin-type heat sink needs to be further improved. For example, it is important to introduce the ambient airflow into the heat sink more easily while guiding the airflow to the heated surfaces to remove the heat from the heat generation components. Moreover, after the airflow is introduced into the heat sink, it is important to guide the airflow to be away from the heated surface and the heat sink more quickly in order to enhance the heat dissipating efficiency.